A special guest for the final phase of Conor McGregor’s training for his blockbuster boxing bout against Floyd Mayweather this Saturday, veteran referee and Hall of Famer Joe Cortez was responsible for teaching the details of the boxing ruleset to the Irishman. And at the end of six weeks of practice, Cortez seems satisfied with the results he accomplished with the UFC lightweight champion.

Despite rumors that suggested McGregor was going to or should at least try to play outside of the rules – from trying to just stretch the rules with dirty tactics to flat-out kicking Mayweather in the head –, Cortez is confident that McGregor will be as clean as it gets when he steps into the boxing ring.

“I made sure he studied every aspect of the game. He’s a great student, he learns fast, we were surprised how fast he learns. I’ve been making sure he was following the rules [during sparring sessions] and he’s going to follow 100% of them.”

Working for the first time with someone trying to cross over to boxing from MMA, Cortez praised McGregor’s performance but also made it a point to emphasize that any other high-level athlete who wants to change sports like that should think about hiring a specialized referee.

“When an MMA fighter moves to boxing, that’s a big difference for them because they don’t know the rules that are applied in boxing”, Cortez said. “So, they called me to teach him all the specific rules and his team got in touch with me. They wanted someone with experience in that game and I was honored to be chosen for this job.”

McGregor will make his professional boxing debut when he meets 49-0 former five-time champion Floyd Mayweather in the ring on Saturday. The fight that, according to some suggestions, might break the five-million mark in PPV buys will take place inside T-Mobile Arena in Las Vegas, Nevada.